1
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Ngo VN, Winski DP, Aho B, Kamath PL, King BL, Waters H, Zimmerberg J, Sodt A, Hess ST. Conserved sequence features in intracellular domains of viral spike proteins. Virology 2024; 599:110198. [PMID: 39116647 PMCID: PMC11383743 DOI: 10.1016/j.virol.2024.110198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2024] [Revised: 07/23/2024] [Accepted: 07/31/2024] [Indexed: 08/10/2024]
Abstract
Viral spike proteins mutate frequently, but conserved features within these proteins often have functional importance and can inform development of anti-viral therapies which circumvent the effects of viral sequence mutations. Through analysis of large numbers of viral spike protein sequences from several viral families, we found highly (>99%) conserved patterns within their intracellular domains. The patterns generally consist of one or more basic amino acids (arginine or lysine) adjacent to a cysteine, many of which are known to undergo acylation. These patterns were not enriched in cellular proteins in general. Molecular dynamics simulations show direct electrostatic and hydrophobic interactions between these conserved residues in hemagglutinin (HA) from influenza A and B and the phosphoinositide PIP2. Super-resolution microscopy shows nanoscale colocalization of PIP2 and several of the same viral proteins. We propose the hypothesis that these conserved viral spike protein features can interact with phosphoinositides such as PIP2.
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Affiliation(s)
- Vinh-Nhan Ngo
- Department of Physics and Astronomy, 120 Bennett Hall, University of Maine, Orono, ME, 04469-5709, USA
| | - David P Winski
- Department of Physics and Astronomy, 120 Bennett Hall, University of Maine, Orono, ME, 04469-5709, USA
| | - Brandon Aho
- Department of Physics and Astronomy, 120 Bennett Hall, University of Maine, Orono, ME, 04469-5709, USA
| | - Pauline L Kamath
- School of Food and Agriculture, 342 Hitchner Hall, University of Maine, And Maine Center for Genetics in the Environment, Orono, ME, USA.
| | - Benjamin L King
- Department of Molecular and Biomedical Sciences, 5735 Hitchner Hall, University of Maine, Orono, ME, USA.
| | - Hang Waters
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Joshua Zimmerberg
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Alexander Sodt
- Unit on Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Samuel T Hess
- Department of Physics and Astronomy, 120 Bennett Hall, University of Maine, Orono, ME, 04469-5709, USA.
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2
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Kephart SM, Hom N, Lee KK. Visualizing intermediate stages of viral membrane fusion by cryo-electron tomography. Trends Biochem Sci 2024; 49:916-931. [PMID: 39054240 PMCID: PMC11455608 DOI: 10.1016/j.tibs.2024.06.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 06/07/2024] [Accepted: 06/18/2024] [Indexed: 07/27/2024]
Abstract
Protein-mediated membrane fusion is the dynamic process where specialized protein machinery undergoes dramatic conformational changes that drive two membrane bilayers together, leading to lipid mixing and opening of a fusion pore between previously separate membrane-bound compartments. Membrane fusion is an essential stage of enveloped virus entry that results in viral genome delivery into host cells. Recent studies applying cryo-electron microscopy techniques in a time-resolved fashion provide unprecedented glimpses into the interaction of viral fusion proteins and membranes, revealing fusion intermediate states from the initiation of fusion to release of the viral genome. In combination with complementary structural, biophysical, and computation modeling approaches, these advances are shedding new light on the mechanics and dynamics of protein-mediated membrane fusion.
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Affiliation(s)
- Sally M Kephart
- Department of Medicinal Chemistry, University of Washington, Seattle, WA, USA
| | - Nancy Hom
- Department of Medicinal Chemistry, University of Washington, Seattle, WA, USA
| | - Kelly K Lee
- Department of Medicinal Chemistry, University of Washington, Seattle, WA, USA; Biological Structure Physics and Design Graduate Program, University of Washington, Seattle, WA, USA.
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3
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Dey S, Pahari P, Mukherjee S, Munro JB, Das DK. Conformational dynamics of SARS-CoV-2 Omicron spike trimers during fusion activation at single molecule resolution. Structure 2024:S0969-2126(24)00377-0. [PMID: 39366371 DOI: 10.1016/j.str.2024.09.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Revised: 07/26/2024] [Accepted: 09/09/2024] [Indexed: 10/06/2024]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron entry involves spike (S) glycoprotein-mediated fusion of viral and late endosomal membranes. Here, using single-molecule Förster resonance energy transfer (sm-FRET) imaging and biochemical measurements, we directly visualized conformational changes of individual spike trimers on the surface of SARS-CoV-2 Omicron pseudovirions during fusion activation. We observed that the S2 domain of the Omicron spike is a dynamic fusion machine. S2 reversibly interchanges between the pre-fusion conformation and two previously undescribed intermediate conformations. Acidic pH shifts the conformational equilibrium of S2 toward an intermediate conformation and promotes the membrane hemi-fusion reaction. Moreover, we captured conformational reversibility in the S2 domain, which suggests that spike can protect itself from pre-triggering. Furthermore, we determined that Ca2+ directly promotes the S2 conformational change from an intermediate conformation to post-fusion conformation. In the presence of a target membrane, low pH and Ca2+ stimulate the irreversible transition to S2 post-fusion state and promote membrane fusion.
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Affiliation(s)
- Shuvankar Dey
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
| | - Purba Pahari
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
| | - Srija Mukherjee
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
| | - James B Munro
- Department of Microbiology, University of Massachusetts Chan Medical School, Worcester, MA, USA; Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Dibyendu Kumar Das
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India; Center for Engineering in Medicine, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India.
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4
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Bhattacharya A, Bagheri N, Boxer SG. A Fluorogenic Pseudoinfection Assay to Probe Transfer and Distribution of Influenza Viral Contents to Target Vesicles. Anal Chem 2024. [PMID: 39086018 DOI: 10.1021/acs.analchem.4c01142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2024]
Abstract
Fusion of enveloped viruses with endosomal membranes and subsequent release of the viral genome into the cytoplasm are crucial to the viral infection cycle. It is often modeled by performing fusion between virus particles and target lipid vesicles. We utilized fluorescence microscopy to characterize the kinetic aspects of the transfer of influenza viral ribonucleoprotein (vRNP) complexes to target vesicles and their spatial distribution within the fused volumes to gain deeper insight into the mechanistic aspects of endosomal escape. The fluorogenic RNA-binding dye QuantiFluor (Promega) was found to be well-suited for direct and sensitive microscopic observation of vRNPs which facilitated background-free detection and kinetic analysis of fusion events on a single particle level. To determine the extent to which the viral contents are transferred to the target vesicles through the fusion pore, we carried out virus-vesicle fusion in a side-by-side fashion. Measurement of the Euclidean distances between the centroids of superlocalized membrane and content dye signals within the fused volumes allowed determination of any symmetry (or the lack thereof) between them as expected in the event of transfer (or the lack thereof) of vRNPs, respectively. We found that, in the case of fusion between viruses and 100 nm target vesicles, ∼39% of the events led to transfer of viral contents to the target vesicles. This methodology provides a rapid, generic, and cell-free way to assess the inhibitory effects of antiviral drugs and therapeutics on the endosomal escape behavior of enveloped viruses.
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Affiliation(s)
- Ahanjit Bhattacharya
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Stanford Center for Innovation in Global Health, Stanford University, Stanford, California 94305, United States
| | - Nahal Bagheri
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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5
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Selivanovitch E, Ostwalt A, Chao Z, Daniel S. Emerging Designs and Applications for Biomembrane Biosensors. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2024; 17:339-366. [PMID: 39018354 DOI: 10.1146/annurev-anchem-061622-042618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/19/2024]
Abstract
Nature has inspired the development of biomimetic membrane sensors in which the functionalities of biological molecules, such as proteins and lipids, are harnessed for sensing applications. This review provides an overview of the recent developments for biomembrane sensors compatible with either bulk or planar sensing applications, namely using lipid vesicles or supported lipid bilayers, respectively. We first describe the individual components required for these sensing platforms and the design principles that are considered when constructing them, and we segue into recent applications being implemented across multiple fields. Our goal for this review is to illustrate the versatility of nature's biomembrane toolbox and simultaneously highlight how biosensor platforms can be enhanced by harnessing it.
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Affiliation(s)
- Ekaterina Selivanovitch
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA;
| | - Alexis Ostwalt
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA;
| | - Zhongmou Chao
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA;
| | - Susan Daniel
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA;
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6
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Velez-Brochero M, Behera P, Afreen KS, Odle A, Rajsbaum R. Ubiquitination in viral entry and replication: Mechanisms and implications. Adv Virus Res 2024; 119:1-38. [PMID: 38897707 DOI: 10.1016/bs.aivir.2024.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
The ubiquitination process is a reversible posttranslational modification involved in many essential cellular functions, such as innate immunity, cell signaling, trafficking, protein stability, and protein degradation. Viruses can use the ubiquitin system to efficiently enter host cells, replicate and evade host immunity, ultimately enhancing viral pathogenesis. Emerging evidence indicates that enveloped viruses can carry free (unanchored) ubiquitin or covalently ubiquitinated viral structural proteins that can increase the efficiency of viral entry into host cells. Furthermore, viruses continuously evolve and adapt to take advantage of the host ubiquitin machinery, highlighting its importance during virus infection. This review discusses the battle between viruses and hosts, focusing on how viruses hijack the ubiquitination process at different steps of the replication cycle, with a specific emphasis on viral entry. We discuss how ubiquitination of viral proteins may affect tropism and explore emerging therapeutics strategies targeting the ubiquitin system for antiviral drug discovery.
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Affiliation(s)
- Maria Velez-Brochero
- Center for Virus-Host-Innate Immunity and Department of Medicine, Rutgers Biomedical and Health Sciences, Institute for Infectious and Inflammatory Diseases, Rutgers University, Newark, NJ, United States
| | - Padmanava Behera
- Center for Virus-Host-Innate Immunity and Department of Medicine, Rutgers Biomedical and Health Sciences, Institute for Infectious and Inflammatory Diseases, Rutgers University, Newark, NJ, United States
| | - Kazi Sabrina Afreen
- Center for Virus-Host-Innate Immunity and Department of Medicine, Rutgers Biomedical and Health Sciences, Institute for Infectious and Inflammatory Diseases, Rutgers University, Newark, NJ, United States
| | - Abby Odle
- Center for Virus-Host-Innate Immunity and Department of Medicine, Rutgers Biomedical and Health Sciences, Institute for Infectious and Inflammatory Diseases, Rutgers University, Newark, NJ, United States
| | - Ricardo Rajsbaum
- Center for Virus-Host-Innate Immunity and Department of Medicine, Rutgers Biomedical and Health Sciences, Institute for Infectious and Inflammatory Diseases, Rutgers University, Newark, NJ, United States.
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7
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Nguyen KT, Rima XY, Nguyen LTH, Wang X, Kwak KJ, Yoon MJ, Li H, Chiang CL, Doon-Ralls J, Scherler K, Fallen S, Godfrey SL, Wallick JA, Magaña SM, Palmer AF, Lee I, Nunn CC, Reeves KM, Kaplan HG, Goldman JD, Heath JR, Wang K, Pancholi P, Lee LJ, Reátegui E. Integrated Antigenic and Nucleic Acid Detection in Single Virions and Extracellular Vesicles with Viral Content. Adv Healthc Mater 2024:e2400622. [PMID: 38820600 DOI: 10.1002/adhm.202400622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2024] [Revised: 05/06/2024] [Indexed: 06/02/2024]
Abstract
Virion-mediated outbreaks are imminent and despite rapid responses, continue to cause adverse symptoms and death. Therefore, tunable, sensitive, high-throughput assays are needed to help diagnose future virion-mediated outbreaks. Herein, it is developed a tunable in situ assay to selectively enrich virions and extracellular vesicles (EVs) and simultaneously detect antigens and nucleic acids at a single-particle resolution. The Biochip Antigen and RNA Assay (BARA) enhanced sensitivities compared to quantitative reverse-transcription polymerase chain reaction (qRT-PCR), enabling the detection of virions in asymptomatic patients, genetic mutations in single virions, and enabling the continued long-term expression of viral RNA in the EV-enriched subpopulation in the plasma of patients with post-acute sequelae of the coronavirus disease of 2019 (COVID-19). BARA revealed highly accurate diagnoses of COVID-19 by simultaneously detecting the spike glycoprotein and nucleocapsid-encoding RNA in saliva and nasopharyngeal swab samples. Altogether, the single-particle detection of antigens and viral RNA provides a tunable framework for the diagnosis, monitoring, and mutation screening of current and future outbreaks.
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Affiliation(s)
- Kim Truc Nguyen
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | - Xilal Y Rima
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
- Diabetes and Metabolism Research Center, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Luong T H Nguyen
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | - Xinyu Wang
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | | | - Min Jin Yoon
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | - Hong Li
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | - Chi-Ling Chiang
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | - Jacob Doon-Ralls
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | | | | | | | | | - Setty M Magaña
- Translational Neuroimmunology, Center for Clinical and Translational Research, Nationwide Children's Hospital, Columbus, OH, 43205, USA
| | - Andre F Palmer
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | - Inyoul Lee
- Institute for Systems Biology, Seattle, WA, 98109, USA
| | | | | | - Henry G Kaplan
- Providence Swedish Cancer Institute, Seattle, WA, 98104, USA
| | - Jason D Goldman
- Providence Swedish Medical Center, Seattle, WA, 98104, USA
- Division of Allergy and Infectious Diseases, University of Washington, Seattle, WA, 98195, USA
| | - James R Heath
- Institute for Systems Biology, Seattle, WA, 98109, USA
| | - Kai Wang
- Institute for Systems Biology, Seattle, WA, 98109, USA
| | - Preeti Pancholi
- Department of Pathology, The Ohio State University Wexner Medical Center, Columbus, OH, 43203, USA
| | - L James Lee
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | - Eduardo Reátegui
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, 43210, USA
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8
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Liu HY, Hu Y, Yu C, Wang ZG, Liu SL, Pang DW. Quantitative single-virus tracking for revealing the dynamics of SARS-CoV-2 fusion with plasma membrane. Sci Bull (Beijing) 2024; 69:502-511. [PMID: 37993331 DOI: 10.1016/j.scib.2023.11.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 10/12/2023] [Accepted: 11/03/2023] [Indexed: 11/24/2023]
Abstract
Viral envelope fusion with the host plasma membrane (PM) for genome release is a hallmark step in the life cycle of many enveloped viruses. This process is regulated by a complex network of biomolecules on the PM, but robust tools to precisely elucidate the dynamic mechanisms of virus-PM fusion events are still lacking. Here, we developed a quantitative single-virus tracking approach based on highly efficient dual-color labelling of viruses and batch trajectory analysis to achieve the spatiotemporal quantification of fusion events. This approach allows us to comprehensively analyze the membrane fusion mechanism utilized by pseudotyped severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the single-virus level and precisely elucidate how the relevant biomolecules synergistically regulate the fusion process. Our results revealed that SARS-CoV-2 may promote the formation of supersaturated clusters of cholesterol to facilitate the initiation of the membrane fusion process and accelerate the viral genome release.
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Affiliation(s)
- Hao-Yang Liu
- State Key Laboratory of Medicinal Chemical Biology, Frontiers Science Center for New Organic Matter, Frontiers Science Center for Cell Responses, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin 300071, China
| | - Yusi Hu
- State Key Laboratory of Medicinal Chemical Biology, Frontiers Science Center for New Organic Matter, Frontiers Science Center for Cell Responses, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin 300071, China
| | - Cong Yu
- State Key Laboratory of Medicinal Chemical Biology, Frontiers Science Center for New Organic Matter, Frontiers Science Center for Cell Responses, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin 300071, China
| | - Zhi-Gang Wang
- State Key Laboratory of Medicinal Chemical Biology, Frontiers Science Center for New Organic Matter, Frontiers Science Center for Cell Responses, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin 300071, China
| | - Shu-Lin Liu
- State Key Laboratory of Medicinal Chemical Biology, Frontiers Science Center for New Organic Matter, Frontiers Science Center for Cell Responses, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin 300071, China; Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, China.
| | - Dai-Wen Pang
- State Key Laboratory of Medicinal Chemical Biology, Frontiers Science Center for New Organic Matter, Frontiers Science Center for Cell Responses, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin 300071, China; Haihe Laboratory of Sustainable Chemical Transformations, Tianjin 300192, China.
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9
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Bottacchiari M, Gallo M, Bussoletti M, Casciola CM. The local variation of the Gaussian modulus enables different pathways for fluid lipid vesicle fusion. Sci Rep 2024; 14:23. [PMID: 38168475 PMCID: PMC10762093 DOI: 10.1038/s41598-023-50922-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 12/28/2023] [Indexed: 01/05/2024] Open
Abstract
Viral infections, fertilization, neurotransmission, and many other fundamental biological processes rely on membrane fusion. Straightforward calculations based on the celebrated Canham-Helfrich elastic model predict a large topological energy barrier that prevents the fusion process from being thermally activated. While such high energy is in accordance with the physical barrier function of lipid membranes, it is difficult to reconcile with the biological mechanisms involved in fusion processes. In this work, we use a Ginzburg-Landau type of free energy that recovers the Canham-Helfrich model in the limit of small width-to-vesicle-extension ratio, with the additional ability to handle topological transitions. We show that a local modification of the Gaussian modulus in the merging region both dramatically lowers the elastic energy barrier and substantially changes the minimal energy pathway for fusion, in accordance with experimental evidence. Therefore, we discuss biological examples in which such a modification might play a crucial role.
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Affiliation(s)
- Matteo Bottacchiari
- Department of Mechanical and Aerospace Engineering, Sapienza Università di Roma, Rome, Italy
| | - Mirko Gallo
- Department of Mechanical and Aerospace Engineering, Sapienza Università di Roma, Rome, Italy
| | - Marco Bussoletti
- Department of Mechanical and Aerospace Engineering, Sapienza Università di Roma, Rome, Italy
| | - Carlo Massimo Casciola
- Department of Mechanical and Aerospace Engineering, Sapienza Università di Roma, Rome, Italy.
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10
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Ramirez JM, Calderon-Zavala AC, Balaram A, Heldwein EE. In vitro reconstitution of herpes simplex virus 1 fusion identifies low pH as a fusion co-trigger. mBio 2023; 14:e0208723. [PMID: 37874146 PMCID: PMC10746285 DOI: 10.1128/mbio.02087-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 09/11/2023] [Indexed: 10/25/2023] Open
Abstract
IMPORTANCE HSV-1 causes lifelong, incurable infections and diseases ranging from mucocutaneous lesions to fatal encephalitis. Fusion of viral and host membranes is a critical step in HSV-1 infection of target cells that requires multiple factors on both the viral and host sides. Due to this complexity, many fundamental questions remain unanswered, such as the identity of the viral and host factors that are necessary and sufficient for HSV-1-mediated membrane fusion and the nature of the fusion trigger. Here, we developed a simplified in vitro fusion assay to examine the fusion requirements and identified low pH as a co-trigger for virus-mediated fusion in vitro. We hypothesize that low pH has a critical role in cell entry and, potentially, pathogenesis.
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Affiliation(s)
- J. Martin Ramirez
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
- Medical Scientist Training Program, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ariana C. Calderon-Zavala
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ariane Balaram
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ekaterina E. Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
- Medical Scientist Training Program, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
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11
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Sharma A, Negi G, Chaudhary M, Parveen N. Kinetics of Ganglioside-Rich Supported Lipid Bilayer Formation with Tracer Vesicle Fluorescence Imaging. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:11694-11707. [PMID: 37552772 DOI: 10.1021/acs.langmuir.3c01301] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/10/2023]
Abstract
Gangliosides, forming a class of lipids complemented by sugar chains, influence the lateral distribution of membrane proteins or membrane-binding proteins, act as receptors for viruses and bacterial toxins, and mediate several types of cellular signaling. Gangliosides incorporated into supported lipid bilayers (SLBs) have been widely applied as a model system to examine these biological processes. In this work, we explored how ganglioside composition affects the kinetics of SLB formation using the vesicle rupturing method on a solid surface. We imaged the attachment of vesicles and the subsequent SLB formation using the time-lapse total internal reflection fluorescence microscopy technique. In the early phase, the ganglioside type and concentration influence the adsorption kinetics of vesicles and their residence/lifetime on the surface before rupturing. Our data confirm that a simultaneous rupturing of neighboring surface-adsorbed vesicles forms microscopic lipid patches on the surface and it is triggered by a critical coverage of the vesicles independent of their composition. In the SLB growth phase, lipid patches merge, forming a continuous SLB. The propagation of patch edges catalyzes the process and depends on the ganglioside type. Our pH-dependent experiments confirm that the polar/charged head groups of the gangliosides have a critical role in these steps and phases of SLB formation kinetics.
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Affiliation(s)
- Anurag Sharma
- Department of Chemistry, Indian Institute of Technology Kanpur, 208016 Kanpur, India
| | - Geetanjali Negi
- Department of Chemistry, Indian Institute of Technology Kanpur, 208016 Kanpur, India
| | - Monika Chaudhary
- Department of Chemistry, Indian Institute of Technology Kanpur, 208016 Kanpur, India
| | - Nagma Parveen
- Department of Chemistry, Indian Institute of Technology Kanpur, 208016 Kanpur, India
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12
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Xie E, Ahmad S, Smyth RP, Sieben C. Advanced fluorescence microscopy in respiratory virus cell biology. Adv Virus Res 2023; 116:123-172. [PMID: 37524480 DOI: 10.1016/bs.aivir.2023.05.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2023]
Abstract
Respiratory viruses are a major public health burden across all age groups around the globe, and are associated with high morbidity and mortality rates. They can be transmitted by multiple routes, including physical contact or droplets and aerosols, resulting in efficient spreading within the human population. Investigations of the cell biology of virus replication are thus of utmost importance to gain a better understanding of virus-induced pathogenicity and the development of antiviral countermeasures. Light and fluorescence microscopy techniques have revolutionized investigations of the cell biology of virus infection by allowing the study of the localization and dynamics of viral or cellular components directly in infected cells. Advanced microscopy including high- and super-resolution microscopy techniques available today can visualize biological processes at the single-virus and even single-molecule level, thus opening a unique view on virus infection. We will highlight how fluorescence microscopy has supported investigations on virus cell biology by focusing on three major respiratory viruses: respiratory syncytial virus (RSV), Influenza A virus (IAV) and SARS-CoV-2. We will review our current knowledge of virus replication and highlight how fluorescence microscopy has helped to improve our state of understanding. We will start by introducing major imaging and labeling modalities and conclude the chapter with a perspective discussion on remaining challenges and potential opportunities.
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Affiliation(s)
- Enyu Xie
- Nanoscale Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Shazeb Ahmad
- Helmholtz Institute for RNA-based Infection Research, Helmholtz Centre for Infection Research, Würzburg, Germany
| | - Redmond P Smyth
- Helmholtz Institute for RNA-based Infection Research, Helmholtz Centre for Infection Research, Würzburg, Germany; Faculty of Medicine, University of Würzburg, Würzburg, Germany
| | - Christian Sieben
- Nanoscale Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany; Institute of Genetics, Technische Universität Braunschweig, Braunschweig, Germany.
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13
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Cervantes M, Hess T, Morbioli GG, Sengar A, Kasson PM. The ACE2 receptor accelerates but is not biochemically required for SARS-CoV-2 membrane fusion. Chem Sci 2023; 14:6997-7004. [PMID: 37389252 PMCID: PMC10306070 DOI: 10.1039/d2sc06967a] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 06/05/2023] [Indexed: 07/01/2023] Open
Abstract
The SARS-CoV-2 coronavirus infects human cells via the ACE2 receptor. Structural evidence suggests that ACE2 may not just serve as an attachment factor but also conformationally activate the SARS-CoV-2 spike protein for membrane fusion. Here, we test that hypothesis directly, using DNA-lipid tethering as a synthetic attachment factor in place of ACE2. We find that SARS-CoV-2 pseudovirus and virus-like particles are capable of membrane fusion without ACE2 if activated with an appropriate protease. Thus, ACE2 is not biochemically required for SARS-CoV-2 membrane fusion. However, addition of soluble ACE2 speeds up the fusion reaction. On a per-spike level, ACE2 appears to promote activation for fusion and then subsequent inactivation if an appropriate protease is not present. Kinetic analysis suggests at least two rate-limiting steps for SARS-CoV-2 membrane fusion, one of which is ACE2 dependent and one of which is not. Since ACE2 serves as a high-affinity attachment factor on human cells, the possibility to replace it with other factors implies a flatter fitness landscape for host adaptation by SARS-CoV-2 and future related coronaviruses.
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Affiliation(s)
- Marcos Cervantes
- Departments of Molecular Physiology and Biomedical Engineering, University of Virginia Charlottesville VA 22908 USA
| | - Tobin Hess
- Departments of Molecular Physiology and Biomedical Engineering, University of Virginia Charlottesville VA 22908 USA
| | - Giorgio G Morbioli
- Departments of Molecular Physiology and Biomedical Engineering, University of Virginia Charlottesville VA 22908 USA
| | - Anjali Sengar
- Departments of Molecular Physiology and Biomedical Engineering, University of Virginia Charlottesville VA 22908 USA
| | - Peter M Kasson
- Departments of Molecular Physiology and Biomedical Engineering, University of Virginia Charlottesville VA 22908 USA
- Science for Life Laboratory and Department of Molecular and Cellular Biology, Uppsala University Uppsala SE 75123 USA
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14
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Liu D, Pan L, Zhai H, Qiu HJ, Sun Y. Virus tracking technologies and their applications in viral life cycle: research advances and future perspectives. Front Immunol 2023; 14:1204730. [PMID: 37334362 PMCID: PMC10272434 DOI: 10.3389/fimmu.2023.1204730] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 05/22/2023] [Indexed: 06/20/2023] Open
Abstract
Viruses are simple yet highly pathogenic microorganisms that parasitize within cells and pose serious threats to the health, economic development, and social stability of both humans and animals. Therefore, it is crucial to understand the dynamic mechanism of virus infection in hosts. One effective way to achieve this is through virus tracking technology, which utilizes fluorescence imaging to track the life processes of virus particles in living cells in real-time, providing a comprehensively and detailed spatiotemporal dynamic process and mechanism of virus infection. This paper provides a broad overview of virus tracking technology, including the selection of fluorescent labels and virus labeling components, the development of imaging microscopes, and its applications in various virus studies. Additionally, we discuss the possibilities and challenges of its future development, offering theoretical guidance and technical support for effective prevention and control of the viral disease outbreaks and epidemics.
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Affiliation(s)
| | | | | | - Hua-Ji Qiu
- *Correspondence: Hua-Ji Qiu, ; Yuan Sun,
| | - Yuan Sun
- *Correspondence: Hua-Ji Qiu, ; Yuan Sun,
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15
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Sengar A, Cervantes M, Bondalapati ST, Hess T, Kasson PM. Single-Virus Fusion Measurements Reveal Multiple Mechanistically Equivalent Pathways for SARS-CoV-2 Entry. J Virol 2023; 97:e0199222. [PMID: 37133381 PMCID: PMC10231210 DOI: 10.1128/jvi.01992-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 04/11/2023] [Indexed: 05/04/2023] Open
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) binds to cell surface receptors and is activated for membrane fusion and cell entry via proteolytic cleavage. Phenomenological data have shown that SARS-CoV-2 can be activated for entry at either the cell surface or in endosomes, but the relative roles in different cell types and mechanisms of entry have been debated. Here, we used single-virus fusion experiments and exogenously controlled proteases to probe activation directly. We found that plasma membrane and an appropriate protease are sufficient to support SARS-CoV-2 pseudovirus fusion. Furthermore, fusion kinetics of SARS-CoV-2 pseudoviruses are indistinguishable no matter which of a broad range of proteases is used to activate the virus. This suggests that the fusion mechanism is insensitive to protease identity or even whether activation occurs before or after receptor binding. These data support a model for opportunistic fusion by SARS-CoV-2 in which the subcellular location of entry likely depends on the differential activity of airway, cellsurface, and endosomal proteases, but all support infection. Inhibition of any single host protease may thus reduce infection in some cells but may be less clinically robust. IMPORTANCE SARS-CoV-2 can use multiple pathways to infect cells, as demonstrated recently when new viral variants switched dominant infection pathways. Here, we used single-virus fusion experiments together with biochemical reconstitution to show that these multiple pathways coexist simultaneously and specifically that the virus can be activated by different proteases in different cellular compartments with mechanistically identical effects. The consequences of this are that the virus is evolutionarily plastic and that therapies targeting viral entry should address multiple pathways at once to achieve optimal clinical effects.
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Affiliation(s)
- Anjali Sengar
- Department of Molecular Physiology, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
| | - Marcos Cervantes
- Department of Molecular Physiology, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
| | - Sai T. Bondalapati
- Department of Molecular Physiology, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
| | - Tobin Hess
- Department of Molecular Physiology, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
| | - Peter M. Kasson
- Department of Molecular Physiology, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, Global Infectious Diseases Institute, University of Virginia, Charlottesville, Virginia, USA
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
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16
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Golani G, Schwarz US. High curvature promotes fusion of lipid membranes: Predictions from continuum elastic theory. Biophys J 2023; 122:1868-1882. [PMID: 37077047 PMCID: PMC10209146 DOI: 10.1016/j.bpj.2023.04.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 03/19/2023] [Accepted: 04/14/2023] [Indexed: 04/21/2023] Open
Abstract
The fusion of lipid membranes progresses through a series of hemifusion intermediates with two significant energy barriers related to the formation of stalk and fusion pore, respectively. These energy barriers determine the speed and success rate of many critical biological processes, including the fusion of highly curved membranes, for example synaptic vesicles and enveloped viruses. Here we use continuum elastic theory of lipid monolayers to determine the relationship between membrane shape and energy barriers to fusion. We find that the stalk formation energy decreases with curvature by up to 31 kBT in a 20-nm-radius vesicle compared with planar membranes and by up to 8 kBT in the fusion of highly curved, long, tubular membranes. In contrast, the fusion pore formation energy barrier shows a more complicated behavior. Immediately after stalk expansion to the hemifusion diaphragm, the fusion pore formation energy barrier is low (15-25 kBT) due to lipid stretching in the distal monolayers and increased tension in highly curved vesicles. Therefore, the opening of the fusion pore is faster. However, these stresses relax over time due to lipid flip-flop from the proximal monolayer, resulting in a larger hemifusion diaphragm and a higher fusion pore formation energy barrier, up to 35 kBT. Therefore, if the fusion pore fails to open before significant lipid flip-flop takes place, the reaction proceeds to an extended hemifusion diaphragm state, which is a dead-end configuration in the fusion process and can be used to prevent viral infections. In contrast, in the fusion of long tubular compartments, the surface tension does not accumulate due to the formation of the diaphragm, and the energy barrier for pore expansion increases with curvature by up to 11 kBT. This suggests that inhibition of polymorphic virus infection could particularly target this feature of the second barrier.
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Affiliation(s)
- Gonen Golani
- Institute for Theoretical Physics and BioQuant Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany
| | - Ulrich S Schwarz
- Institute for Theoretical Physics and BioQuant Center for Quantitative Biology, Heidelberg University, Heidelberg, Germany.
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17
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Chien YAA, Alford BK, Wasik BR, Weichert WS, Parrish CR, Daniel S. Single Particle Analysis of H3N2 Influenza Entry Differentiates the Impact of the Sialic Acids (Neu5Ac and Neu5Gc) on Virus Binding and Membrane Fusion. J Virol 2023; 97:e0146322. [PMID: 36779754 PMCID: PMC10062150 DOI: 10.1128/jvi.01463-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 01/18/2023] [Indexed: 02/14/2023] Open
Abstract
Entry of influenza A viruses (IAVs) into host cells is initiated by binding to sialic acids (Sias), their primary host cell receptor, followed by endocytosis and membrane fusion to release the viral genome into the cytoplasm of the host cell. Host tropism is affected by these entry processes, with a primary factor being receptor specificity. Sias exist in several different chemical forms, including the hydroxylated N-glycolylneuraminic acid (Neu5Gc), which is found in many hosts; however, it has not been clear how modified Sias affect viral binding and entry. Neu5Gc is commonly found in many natural influenza hosts, including pigs and horses, but not in humans or ferrets. Here, we engineered HEK293 cells to express the hydoxylase gene (CMAH) that converts Neu5Ac to Neu5Gc, or knocked out the Sia-CMP transport gene (SLC35A1), resulting in cells that express 95% Neu5Gc or minimal level of Sias, respectively. H3N2 (X-31) showed significantly reduced infectivity in Neu5Gc-rich cells compared to wild-type HEK293 (>95% Neu5Ac). To determine the effects on binding and fusion, we generated supported lipid bilayers (SLBs) derived from the plasma membranes of these cells and carried out single particle microscopy. H3N2 (X-31) exhibited decreased binding to Neu5Gc-containing SLBs, but no significant difference in H3N2 (X-31)'s fusion kinetics to either SLB type, suggesting that reduced receptor binding does not affect subsequent membrane fusion. This finding suggests that for this virus to adapt to host cells rich in Neu5Gc, only receptor affinity changes are required without further adaptation of virus fusion machinery. IMPORTANCE Influenza A virus (IAV) infections continue to threaten human health, causing over 300,000 deaths yearly. IAV infection is initiated by the binding of influenza glycoprotein hemagglutinin (HA) to host cell sialic acids (Sias) and the subsequent viral-host membrane fusion. Generally, human IAVs preferentially bind to the Sia N-acetylneuraminic acid (Neu5Ac). Yet, other mammalian hosts, including pigs, express diverse nonhuman Sias, including N-glycolylneuraminic acid (Neu5Gc). The role of Neu5Gc in human IAV infections in those hosts is not well-understood, and the variant form may play a role in incidents of cross-species transmission and emergence of new epidemic variants. Therefore, it is important to investigate how human IAVs interact with Neu5Ac and Neu5Gc. Here, we use membrane platforms that mimic the host cell surface to examine receptor binding and membrane fusion events of human IAV H3N2. Our findings improve the understanding of viral entry mechanisms that can affect host tropism and virus evolution.
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Affiliation(s)
- Yu-An Annie Chien
- Department of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA
| | - Brynn K. Alford
- Department of Microbiology and Immunology, Cornell University, Ithaca, New York, USA
| | - Brian R. Wasik
- Department of Microbiology and Immunology, Cornell University, Ithaca, New York, USA
| | - Wendy S. Weichert
- Department of Microbiology and Immunology, Cornell University, Ithaca, New York, USA
| | - Colin R. Parrish
- Department of Microbiology and Immunology, Cornell University, Ithaca, New York, USA
| | - Susan Daniel
- Department of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, USA
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18
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Klein S, Golani G, Lolicato F, Lahr C, Beyer D, Herrmann A, Wachsmuth-Melm M, Reddmann N, Brecht R, Hosseinzadeh M, Kolovou A, Makroczyova J, Peterl S, Schorb M, Schwab Y, Brügger B, Nickel W, Schwarz US, Chlanda P. IFITM3 blocks influenza virus entry by sorting lipids and stabilizing hemifusion. Cell Host Microbe 2023; 31:616-633.e20. [PMID: 37003257 DOI: 10.1016/j.chom.2023.03.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 11/15/2022] [Accepted: 03/06/2023] [Indexed: 04/03/2023]
Abstract
Interferon-induced transmembrane protein 3 (IFITM3) inhibits the entry of numerous viruses through undefined molecular mechanisms. IFITM3 localizes in the endosomal-lysosomal system and specifically affects virus fusion with target cell membranes. We found that IFITM3 induces local lipid sorting, resulting in an increased concentration of lipids disfavoring viral fusion at the hemifusion site. This increases the energy barrier for fusion pore formation and the hemifusion dwell time, promoting viral degradation in lysosomes. In situ cryo-electron tomography captured IFITM3-mediated arrest of influenza A virus membrane fusion. Observation of hemifusion diaphragms between viral particles and late endosomal membranes confirmed hemifusion stabilization as a molecular mechanism of IFITM3. The presence of the influenza fusion protein hemagglutinin in post-fusion conformation close to hemifusion sites further indicated that IFITM3 does not interfere with the viral fusion machinery. Collectively, these findings show that IFITM3 induces lipid sorting to stabilize hemifusion and prevent virus entry into target cells.
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Affiliation(s)
- Steffen Klein
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Gonen Golani
- BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany; Institute for Theoretical Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Fabio Lolicato
- Heidelberg University Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany; Department of Physics, University of Helsinki, Helsinki, Finland
| | - Carmen Lahr
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Daniel Beyer
- Heidelberg University Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany
| | - Alexia Herrmann
- Heidelberg University Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany
| | - Moritz Wachsmuth-Melm
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Nina Reddmann
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Romy Brecht
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Mehdi Hosseinzadeh
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Androniki Kolovou
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Jana Makroczyova
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Sarah Peterl
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany
| | - Martin Schorb
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Yannick Schwab
- Electron Microscopy Core Facility, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Britta Brügger
- Heidelberg University Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Heidelberg University, 69120 Heidelberg, Germany
| | - Ulrich S Schwarz
- BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany; Institute for Theoretical Physics, Heidelberg University, 69120 Heidelberg, Germany
| | - Petr Chlanda
- Schaller Research Group, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany; BioQuant Center for Quantitative Biology, Heidelberg University, 69120 Heidelberg, Germany.
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19
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Park S, Cho NJ. Lipid Membrane Interface Viewpoint: From Viral Entry to Antiviral and Vaccine Development. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:1-11. [PMID: 36576966 DOI: 10.1021/acs.langmuir.2c02501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Membrane-enveloped viruses are responsible for most viral pandemics in history, and more effort is needed to advance broadly applicable countermeasures to mitigate the impact of future outbreaks. In this Perspective, we discuss how biosensing techniques associated with lipid model membrane platforms are contributing to improving our mechanistic knowledge of membrane fusion and destabilization that is closely linked to viral entry as well as vaccine and antiviral drug development. A key benefit of these platforms is the simplicity of interpreting the results which can be complemented by other techniques to decipher more complicated biological observations and evaluate the biophysical functionalities that can be correlated to biological activities. Then, we introduce exciting application examples of membrane-targeting antivirals that have been refined over time and will continue to improve based on biophysical insights. Two ways to abrogate the function of viral membranes are introduced here: (1) selective disruption of the viral membrane structure and (2) alteration of the membrane component. While both methods are suitable for broadly useful antivirals, the latter also has the potential to produce an inactivated vaccine. Collectively, we emphasize how biosensing tools based on membrane interfacial science can provide valuable information that could be translated into biomedicines and improve their selectivity and performance.
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Affiliation(s)
- Soohyun Park
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Nam-Joon Cho
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
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20
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Zhang X, Li W, Cui Z. Single-Particle Tracking of Virus Entry in Live Cells. Subcell Biochem 2023; 106:153-168. [PMID: 38159226 DOI: 10.1007/978-3-031-40086-5_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Novel imaging technologies such as single-particle tracking provide tools to study the intricate process of virus infection in host cells. In this chapter, we provide an overview of studies in which single-particle tracking technologies were applied for the analysis of the viral entry pathways in the context of the live host cell. Single-particle tracking techniques have been dependent on advances in the fluorescent labeling microscopy method and image analysis. The mechanistic and kinetic insights offered by this technique will provide a better understanding of virus entry and may lead to a rational design of antiviral interventions.
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Affiliation(s)
- Xiaowei Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Wei Li
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zongqiang Cui
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, China.
- University of Chinese Academy of Sciences, Beijing, China.
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21
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Mannsverk S, Villamil Giraldo AM, Kasson PM. Influenza Virus Membrane Fusion Is Promoted by the Endosome-Resident Phospholipid Bis(monoacylglycero)phosphate. J Phys Chem B 2022; 126:10445-10451. [PMID: 36468619 PMCID: PMC9761668 DOI: 10.1021/acs.jpcb.2c06642] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The phospholipid bis(monoacylglycero)phosphate (BMP) is enriched in late endosomal and endolysosomal membranes and is believed to be involved in membrane deformation and generation of intralumenal vesicles within late endosomes. Previous studies have demonstrated that BMP promotes membrane fusion of several enveloped viruses, but a limited effect has been found on influenza virus. Here, we report the use of single-virus fusion assays to dissect BMP's effect on influenza virus fusion in greater depth. In agreement with prior reports, we found that hemifusion kinetics and efficiency were unaffected by the addition of 10-20 mol % BMP to the target membrane. However, using an assay for fusion pore formation and genome exposure, we found full fusion efficiency to be substantially enhanced by the addition of 10-20 mol % BMP to the target membrane, while the kinetics remained unaffected. By comparing BMP to other negatively charged phospholipids, we found the effect on fusion efficiency mainly attributable to headgroup charge, although we also hypothesize a role for BMP's unusual chemical structure. Our results suggest that BMP function as a permissive factor for a wider range of viruses than previously reported. We hypothesize that BMP may be a general cofactor for endosomal entry of enveloped viruses.
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Affiliation(s)
- Steinar Mannsverk
- Science
for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
| | - Ana M. Villamil Giraldo
- Science
for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
| | - Peter M. Kasson
- Science
for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden,Departments
of Molecular Physiology and Biomedical Engineering, University of Virginia, Charlottesville, Virginia 22908, United States,
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22
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Villamil Giraldo AM, Mannsverk S, Kasson PM. Measuring single-virus fusion kinetics using an assay for nucleic acid exposure. Biophys J 2022; 121:4467-4475. [PMID: 36330566 PMCID: PMC9748363 DOI: 10.1016/j.bpj.2022.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 09/26/2022] [Accepted: 10/31/2022] [Indexed: 11/11/2022] Open
Abstract
The kinetics by which individual enveloped viruses fuse with membranes provide an important window into viral-entry mechanisms. We have developed a real-time assay using fluorescent probes for single-virus genome exposure than can report on stages of viral entry including or subsequent to fusion pore formation and prior to viral genome trafficking. We accomplish this using oxazole yellow nucleic-acid-binding dyes, which can be encapsulated in the lumen of target membranes to permit specific detection of fusion events. Since increased fluorescence of the dye occurs only when it encounters viral genome via a fusion pore and binds, this assay excludes content leakage without fusion. Using this assay, we show that influenza virus fuses with liposomes of different sizes with indistinguishable kinetics by both testing liposomes extruded through pores of different radii and showing that the fusion kinetics of individual liposomes are uncorrelated with the size of the liposome. These results suggest that the starting curvature of such liposomes does not control the rate-limiting steps in influenza entry.
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Affiliation(s)
- Ana M Villamil Giraldo
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Steinar Mannsverk
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Peter M Kasson
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden; Departments of Molecular Physiology and Biomedical Engineering, University of Virginia, Charlottesville, Virginia.
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23
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Stachowiak JC, Kirchhausen T. The beauty of simplicity in membrane biology. Nat Cell Biol 2022; 24:1682-1685. [PMID: 36266490 PMCID: PMC9742310 DOI: 10.1038/s41556-022-01015-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
For the past 40 years, minimal reconstituted systems have helped cell biologists to understand the mechanisms that underlie membrane traffic. Having progressed from minimal synthetic and cell-derived ensembles to direct comparison with living systems, reconstitution is poised for ever more precise and informative understanding of membrane biology.
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Affiliation(s)
- Jeanne C. Stachowiak
- University of Texas at Austin, Department of Biomedical Engineering, Austin, TX, USA,
| | - Tomas Kirchhausen
- Harvard Medical School, Department of Cell Biology, Boston, MA, USA,Harvard Medical School, Department of Pediatrics, Boston, MA, USA
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24
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Haldar S. Recent Developments in Single-Virus Fusion Assay. J Membr Biol 2022; 255:747-755. [PMID: 36173449 DOI: 10.1007/s00232-022-00270-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 09/13/2022] [Indexed: 12/24/2022]
Abstract
Viral infection is a global health hazard. A crucial step in the infection cycle of enveloped viruses is the fusion of viral and host cellular membranes, which permits the transfer of the viral genome to the host cells. Membrane fusion is a ubiquitous process involved in sperm-egg fusion, exocytosis, vesicular trafficking, and viral entry to host cells. While different protein machineries catalyze the diverse fusion processes, the essential step, i.e., merging of two lipid bilayers against a kinetic energy barrier, is the same. Therefore, viral fusion machineries/pathways are not only the sites for antiviral drug development but also serve as model fusogens. Ensemble-based spectroscopic approaches or bulk fusion assays have yielded valuable insights regarding the fusion processes. However, due to the stochastic nature of the fusion events, ensemble-based assays do not permit synchronization of all the fusion events, and the molecular steps leading to fusion pore opening cannot be resolved entirely and correlated with the structural changes in viral fusion proteins. Several single-virus fusion assays have been developed to circumvent these issues. The review describes the recent advancements in single-virus/particle fusion assays using the Influenza virus as a paradigm.
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Affiliation(s)
- Sourav Haldar
- Division of Virus Research and Therapeutics, CSIR-Central Drug Research Institute, Lucknow, Uttar Pradesh, 226031, India. .,Academy of Scientific and Innovative Research, Ghaziabad, Uttar Pradesh, India.
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25
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Armanious A, Gerelli Y, Micciulla S, Pace HP, Welbourn RJL, Sjöberg M, Agnarsson B, Höök F. Probing the Separation Distance between Biological Nanoparticles and Cell Membrane Mimics Using Neutron Reflectometry with Sub-Nanometer Accuracy. J Am Chem Soc 2022; 144:20726-20738. [DOI: 10.1021/jacs.2c08456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Antonius Armanious
- Department of Physics, Chalmers University of Technology, 41296Gothenburg, Sweden
| | - Yuri Gerelli
- Institut Max von Laue-Paul Langevin (ILL), 38042Grenoble, France
- Department of Life and Environmental Sciences, Università Politecnica delle Marche, 60131Ancona, Italy
| | | | - Hudson P. Pace
- Department of Physics, Chalmers University of Technology, 41296Gothenburg, Sweden
| | - Rebecca J. L. Welbourn
- ISIS Facility, STFC, Rutherford Appleton Laboratory, Chilton, Didcot, OxonOX11 0QX, United Kingdom
| | - Mattias Sjöberg
- Department of Physics, Chalmers University of Technology, 41296Gothenburg, Sweden
| | - Björn Agnarsson
- Department of Physics, Chalmers University of Technology, 41296Gothenburg, Sweden
| | - Fredrik Höök
- Department of Physics, Chalmers University of Technology, 41296Gothenburg, Sweden
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26
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Negi G, Sharma A, Dey M, Dhanawat G, Parveen N. Membrane attachment and fusion of HIV-1, influenza A, and SARS-CoV-2: resolving the mechanisms with biophysical methods. Biophys Rev 2022; 14:1109-1140. [PMID: 36249860 PMCID: PMC9552142 DOI: 10.1007/s12551-022-00999-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 09/16/2022] [Indexed: 10/31/2022] Open
Abstract
Attachment to and fusion with cell membranes are two major steps in the replication cycle of many human viruses. We focus on these steps for three enveloped viruses, i.e., HIV-1, IAVs, and SARS-CoV-2. Viral spike proteins drive the membrane attachment and fusion of these viruses. Dynamic interactions between the spike proteins and membrane receptors trigger their specific attachment to the plasma membrane of host cells. A single virion on cell membranes can engage in binding with multiple receptors of the same or different types. Such dynamic and multivalent binding of these viruses result in an optimal attachment strength which in turn leads to their cellular entry and membrane fusion. The latter process is driven by conformational changes of the spike proteins which are also class I fusion proteins, providing the energetics of membrane tethering, bending, and fusion. These viruses exploit cellular and membrane factors in regulating the conformation changes and membrane processes. Herein, we describe the major structural and functional features of spike proteins of the enveloped viruses including highlights on their structural dynamics. The review delves into some of the case studies in the literature discussing the findings on multivalent binding, membrane hemifusion, and fusion of these viruses. The focus is on applications of biophysical tools with an emphasis on single-particle methods for evaluating mechanisms of these processes at the molecular and cellular levels.
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Affiliation(s)
- Geetanjali Negi
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Anurag Sharma
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Manorama Dey
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Garvita Dhanawat
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Nagma Parveen
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
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27
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Mechanistic dissection of antibody inhibition of influenza entry yields unexpected heterogeneity. Biophys J 2022:S0006-3495(22)00864-5. [DOI: 10.1016/j.bpj.2022.10.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 10/10/2022] [Accepted: 10/17/2022] [Indexed: 11/21/2022] Open
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28
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Kreutzberger AJB, Sanyal A, Saminathan A, Bloyet LM, Stumpf S, Liu Z, Ojha R, Patjas MT, Geneid A, Scanavachi G, Doyle CA, Somerville E, Correia RBDC, Di Caprio G, Toppila-Salmi S, Mäkitie A, Kiessling V, Vapalahti O, Whelan SPJ, Balistreri G, Kirchhausen T. SARS-CoV-2 requires acidic pH to infect cells. Proc Natl Acad Sci U S A 2022; 119:e2209514119. [PMID: 36048924 PMCID: PMC9499588 DOI: 10.1073/pnas.2209514119] [Citation(s) in RCA: 53] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 08/03/2022] [Indexed: 12/12/2022] Open
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cell entry starts with membrane attachment and ends with spike (S) protein-catalyzed membrane fusion depending on two cleavage steps, namely, one usually by furin in producing cells and the second by TMPRSS2 on target cells. Endosomal cathepsins can carry out both. Using real-time three-dimensional single-virion tracking, we show that fusion and genome penetration require virion exposure to an acidic milieu of pH 6.2 to 6.8, even when furin and TMPRSS2 cleavages have occurred. We detect the sequential steps of S1-fragment dissociation, fusion, and content release from the cell surface in TMPRRS2-overexpressing cells only when exposed to acidic pH. We define a key role of an acidic environment for successful infection, found in endosomal compartments and at the surface of TMPRSS2-expressing cells in the acidic milieu of the nasal cavity.
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Affiliation(s)
- Alex J. B. Kreutzberger
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, MA 02115
| | - Anwesha Sanyal
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, MA 02115
| | - Anand Saminathan
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, MA 02115
| | - Louis-Marie Bloyet
- Department of Molecular Microbiology, Washington University in Saint Louis, St. Louis, MO 63110
| | - Spencer Stumpf
- Department of Molecular Microbiology, Washington University in Saint Louis, St. Louis, MO 63110
| | - Zhuoming Liu
- Department of Molecular Microbiology, Washington University in Saint Louis, St. Louis, MO 63110
| | - Ravi Ojha
- Department of Virology, Faculty of Medicine, University of Helsinki, Helsinki, 00290 Finland
| | - Markku T. Patjas
- Department of Otorhinolaryngology and Phoniatrics - Head and Neck Surgery, University of Helsinki and Helsinki University Hospital, Helsinki, 00290 Finland
| | - Ahmed Geneid
- Department of Otorhinolaryngology and Phoniatrics - Head and Neck Surgery, University of Helsinki and Helsinki University Hospital, Helsinki, 00290 Finland
| | - Gustavo Scanavachi
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, MA 02115
| | - Catherine A. Doyle
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22903
| | - Elliott Somerville
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, MA 02115
| | - Ricardo Bango Da Cunha Correia
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, MA 02115
| | - Giuseppe Di Caprio
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, MA 02115
- Department of Pediatrics, Harvard Medical School, Boston, MA 02115
| | - Sanna Toppila-Salmi
- Department of Allergy, University of Helsinki and Helsinki University Hospital, Helsinki, 00290 Finland
| | - Antti Mäkitie
- Department of Otorhinolaryngology and Phoniatrics - Head and Neck Surgery, University of Helsinki and Helsinki University Hospital, Helsinki, 00290 Finland
| | - Volker Kiessling
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA 22903
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22903
| | - Olli Vapalahti
- Department of Virology, Faculty of Medicine, University of Helsinki, Helsinki, 00290 Finland
- Department of Veterinary Biosciences, University of Helsinki, Helsinki, 00290 Finland
- Virology and Immunology, Helsinki University Hospital Diagnostic Center, Helsinki, 00290 Finland
| | - Sean P. J. Whelan
- Department of Molecular Microbiology, Washington University in Saint Louis, St. Louis, MO 63110
| | - Giuseppe Balistreri
- Department of Virology, Faculty of Medicine, University of Helsinki, Helsinki, 00290 Finland
- Department of Veterinary Biosciences, University of Helsinki, Helsinki, 00290 Finland
- The Queensland Brain Institute, University of Queensland, Brisbane, 4072 Australia
| | - Tom Kirchhausen
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115
- Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, MA 02115
- Department of Pediatrics, Harvard Medical School, Boston, MA 02115
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29
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Cavalcanti RRM, Lira RB, Riske KA. Membrane Fusion Biophysical Analysis of Fusogenic Liposomes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:10430-10441. [PMID: 35977420 DOI: 10.1021/acs.langmuir.2c01169] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Liposomes represent important drug carrier vehicles in biological systems. A fusogenic liposomal system composed of equimolar mixtures of the cationic lipid DOTAP and the phospholipid DOPE showed high fusion and delivery efficiencies with cells and lipid vesicles. However, aspects of the thermodynamics involving the interaction of these fusogenic liposomes and biomimetic systems remain unclear. Here, we investigate the fusion of this system with large unilamellar vesicles (LUVs) composed of the zwitterionic lipid POPC and increasing fractions of the anionic lipid POPG and up to 30 mol % cholesterol. The focus here is to concomitantly follow changes in size, zeta-potential, and enthalpy binding upon membrane interaction and fusion. Isothermal titration calorimetry (ITC) data showed that membrane fusion in our system is an exothermic process in the absence of cholesterol, suggesting that electrostatic attraction is the driving force for fusion. An endothermic component appeared and eventually dominated the titration at 30 mol % cholesterol, which we propose is caused by membrane fluidification when cholesterol is diluted upon fusion. The inflection points of the ITC data occurred around 0.5-0.7 POPG/DOTAP for all systems, the same stoichiometry for which zeta-potential and dynamic light scattering measurements showed an increase in size coupled with charge neutralization of the system, which is consistent with the fact that fusion in our system is charge-mediated. Microscopy observations of the final mixtures revealed the presence of giant vesicles, which is a clear indication of fusion, coexisting with intermediate-sized objects that could be the result of both fusion and/or aggregation. The results show that the fusion efficiency of the DOTAP:DOPE fusogenic system is modulated by the charge and membrane packing of the acceptor membrane and explain why the system fuses very efficiently with cells.
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Affiliation(s)
- Rafaela R M Cavalcanti
- Departamento de Biofísica, Universidade Federal de São Paulo, CEP 04039-032, São Paulo, Brazil
| | - Rafael B Lira
- Departamento de Biofísica, Universidade Federal de São Paulo, CEP 04039-032, São Paulo, Brazil
| | - Karin A Riske
- Departamento de Biofísica, Universidade Federal de São Paulo, CEP 04039-032, São Paulo, Brazil
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Li Z, Li T, Liu M, Ivanovic T. Hemagglutinin Stability Determines Influenza A Virus Susceptibility to a Broad-Spectrum Fusion Inhibitor Arbidol. ACS Infect Dis 2022; 8:1543-1552. [PMID: 35819162 PMCID: PMC9810120 DOI: 10.1021/acsinfecdis.2c00178] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Understanding mechanisms of resistance to antiviral inhibitors can reveal nuanced features of targeted viral mechanisms and, in turn, lead to improved strategies for inhibitor design. Arbidol is a broad-spectrum antiviral that binds to and prevents the fusion-associated conformational changes in the trimeric influenza A virus (IAV) hemagglutinin (HA). The rate-limiting step during the HA-mediated membrane fusion is the release of the hydrophobic fusion peptides from a conserved pocket on HA. Here, we investigated how destabilizing or stabilizing mutations in or near the fusion peptide affect viral sensitivity to Arbidol. The degree of sensitivity was proportional to the extent of fusion-peptide stability on the prefusion HA: stabilized mutants were more sensitive, and destabilized ones were resistant to Arbidol. Single-virion membrane fusion experiments for representative wild-type (WT) and mutant viruses demonstrated that resistance is a direct consequence of fusion-peptide destabilization not requiring reduced Arbidol binding to HA. Our results support the model whereby the probability of individual HAs extending to engage the target membrane is determined by the composite of two critical forces: a "tug" on the fusion peptide by HA rearrangements near the Arbidol binding site and the key interactions stabilizing the fusion peptide in the prefusion pocket. Arbidol increases and destabilizing mutations decrease the free-energy cost for fusion-peptide release, accounting for the observed resistance. Our findings have broad implications for fusion inhibitor design, viral mechanisms of resistance, and our basic understanding of HA-mediated membrane fusion.
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Xu W, Wang Y, Li L, Qu X, Liu Q, Li T, Wu S, Liao M, Jin N, Du S, Li C. Transmembrane domain of IFITM3 is responsible for its interaction with influenza virus HA 2 subunit. Virol Sin 2022; 37:664-675. [PMID: 35809785 PMCID: PMC9583175 DOI: 10.1016/j.virs.2022.07.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/30/2022] [Indexed: 11/20/2022] Open
Abstract
Interferon-inducible transmembrane protein 3 (IFITM3) inhibits influenza virus infection by blocking viral membrane fusion, but the exact mechanism remains elusive. Here, we investigated the function and key region of IFITM3 in blocking influenza virus entry mediated by hemagglutinin (HA). The restriction of IFITM3 on HA-mediated viral entry was confirmed by pseudovirus harboring HA protein from H5 and H7 influenza viruses. Subcellular co-localization and immunocoprecipitation analyses revealed that IFITM3 partially co-located with the full-length HA protein and could directly interact with HA2 subunit but not HA1 subunit of H5 and H7 virus. Truncated analyses showed that the transmembrane domain of the IFITM3 and HA2 subunit might play an important role in their interaction. Finally, this interaction of IFITM3 was also verified with HA2 subunits from other subtypes of influenza A virus and influenza B virus. Overall, our data demonstrate for the first time a direct interaction between IFITM3 and influenza HA protein via the transmembrane domain, providing a new perspective for further exploring the biological significance of IFITM3 restriction on influenza virus infection or HA-mediated antagonism or escape. IFITM3 interacts with HA2 subunit of hemagglutinin from multiple subtypes of influenza A and B virus. Interaction between IFITM3 and HA2 subunit is mediated by binding to the transmembrane domain of HA. Affinity of IFITM3 intramembrane domain or transmembrane domain to HA2 subunit of H5 and H7 subtype is different. Transmembrane domain of IFITM3 is responsible for its interaction with the HA2 subunit. There are differences in the binding ability of IFITM3 to HA2 from different serotypes.
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Affiliation(s)
- Wang Xu
- College of Veterinary Medicine, Northwest A&F University, Yangling, 712100, China
| | - Yuhang Wang
- Department of Infectious Diseases, The Second Clinical Medical College of Jinan University, Shenzhen, 518020, China
| | - Letian Li
- Research Unit of Key Technologies for Prevention and Control of Virus Zoonoses, Chinese Academy of Medical Sciences, Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Changchun, 130122, China
| | - Xiaoyun Qu
- Key Laboratory of Zoonosis of Ministry of Agriculture, South China Agricultural University, Guangzhou, 510642, China
| | - Quan Liu
- Key Laboratory of Zoonosis of Ministry of Agriculture, South China Agricultural University, Guangzhou, 510642, China
| | - Tiyuan Li
- Department of Infectious Diseases, The Second Clinical Medical College of Jinan University, Shenzhen, 518020, China
| | - Shipin Wu
- Department of Infectious Diseases, The Second Clinical Medical College of Jinan University, Shenzhen, 518020, China
| | - Ming Liao
- Key Laboratory of Zoonosis of Ministry of Agriculture, South China Agricultural University, Guangzhou, 510642, China
| | - Ningyi Jin
- College of Veterinary Medicine, Northwest A&F University, Yangling, 712100, China; Research Unit of Key Technologies for Prevention and Control of Virus Zoonoses, Chinese Academy of Medical Sciences, Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Changchun, 130122, China.
| | - Shouwen Du
- Department of Infectious Diseases, The Second Clinical Medical College of Jinan University, Shenzhen, 518020, China.
| | - Chang Li
- Research Unit of Key Technologies for Prevention and Control of Virus Zoonoses, Chinese Academy of Medical Sciences, Changchun Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Changchun, 130122, China.
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32
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SARS-CoV-2 requires acidic pH to infect cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2022. [PMID: 35702155 PMCID: PMC9196115 DOI: 10.1101/2022.06.09.495472] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
SARS-CoV-2 cell entry starts with membrane attachment and ends with spike-protein (S) catalyzed membrane fusion depending on two cleavage steps, one usually by furin in producing cells and the second by TMPRSS2 on target cells. Endosomal cathepsins can carry out both. Using real-time 3D single virion tracking, we show fusion and genome penetration requires virion exposure to an acidic milieu of pH 6.2-6.8, even when furin and TMPRSS2 cleavages have occurred. We detect the sequential steps of S1-fragment dissociation, fusion, and content release from the cell surface in TMPRRS2 overexpressing cells only when exposed to acidic pH. We define a key role of an acidic environment for successful infection, found in endosomal compartments and at the surface of TMPRSS2 expressing cells in the acidic milieu of the nasal cavity. Significance Statement Infection by SARS-CoV-2 depends upon the S large spike protein decorating the virions and is responsible for receptor engagement and subsequent fusion of viral and cellular membranes allowing release of virion contents into the cell. Using new single particle imaging tools, to visualize and track the successive steps from virion attachment to fusion, combined with chemical and genetic perturbations of the cells, we provide the first direct evidence for the cellular uptake routes of productive infection in multiple cell types and their dependence on proteolysis of S by cell surface or endosomal proteases. We show that fusion and content release always require the acidic environment from endosomes, preceded by liberation of the S1 fragment which depends on ACE2 receptor engagement. One sentence summary Detailed molecular snapshots of the productive infectious entry pathway of SARS-CoV-2 into cells.
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Abstract
SignificanceThe discovery that amphiphilic polymers, similar to phospholipids, can self-assemble to vesicles has inspired numerous applications. For instance, these polymersomes are employed for drug delivery due to their increased chemical and mechanical stability. These polymers can be also mixed with lipids to form the so-called hybrid membranes, which provide further biocompatibility, while new properties emerge. However, the fusion of these hybrids is to date barely explored. Herein, we determined that hybrid vesicles made of poly(dimethylsiloxane)-graft-poly(ethylene oxide) and oppositely charged lipids undergo rapid fusion, surpassing the efficiency in natural membranes. We provide biophysical insights into the mechanism and demonstrate that anionic lipids are not strictly required when the process is employed for the integration of membrane proteins.
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34
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Oshima A, Nakanishi K, Kasai N, Nakashima H, Tsumoto K, Sumitomo K. Mechanism of Budded Virus Envelope Fusion into a Planar Bilayer Lipid Membrane on a SiO 2 Substrate. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:5464-5471. [PMID: 35436122 DOI: 10.1021/acs.langmuir.1c03456] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Artificial planar bilayer lipid membranes (BLMs) are simple models of cellular systems under physically and chemically controlled conditions, and they have been used to investigate membrane protein activity. Baculovirus-budded virus (BV) systems can express recombinant membrane proteins. In this study, aiming for membrane protein reconstitution, we examined the fusion of BVs containing recombinant membrane proteins into artificial planar BLMs on a Si microwell substrate. BV fusion with the BLMs depended on the pH of the solution, and it was enhanced at lower pH. Based on fluorescence recovery after photobleaching (FRAP) measurement, the fusion state of BVs was evaluated, and full fusion at low pH was confirmed. The fluorescent labeling the membrane proteins was also observed in the freestanding part of the BLMs as well as in the supported part. These results demonstrate the effectiveness of BLMs as a platform to examine detailed fusion dynamics of BVs. Furthermore, this study revealed that the fusion of BVs is a promising method for reconstituting membrane proteins to artificial freestanding BLMs for the development of biodevices with which we can examine membrane protein activity.
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Affiliation(s)
- Azusa Oshima
- NTT Basic Research Laboratories and Bio-Medical Informatics Research Center, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan
- NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan
| | - Kohei Nakanishi
- Division of Chemistry for Materials, Graduate School of Engineering, Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514-8507, Japan
| | - Nahoko Kasai
- NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan
| | - Hiroshi Nakashima
- NTT Basic Research Laboratories and Bio-Medical Informatics Research Center, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan
- NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198, Japan
| | - Kanta Tsumoto
- Division of Chemistry for Materials, Graduate School of Engineering, Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514-8507, Japan
| | - Koji Sumitomo
- University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
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35
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Webster ER, Liu KN, Rawle RJ, Boxer SG. Modulating the Influenza A Virus-Target Membrane Fusion Interface With Synthetic DNA-Lipid Receptors. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:2354-2362. [PMID: 35143209 PMCID: PMC9038422 DOI: 10.1021/acs.langmuir.1c03247] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Influenza A virus (IAV) binds to sialylated glycans on the cell membrane before endocytosis and fusion. Cell-surface glycans are highly heterogeneous in length and glycosylation density, which leads to variations in the distance and rigidity with which IAV is held away from the cell membrane. To gain mechanistic insight into how receptor length and rigidity impact the mechanism of IAV entry, we employed synthetic DNA-lipids as highly tunable surrogate receptors. We tethered IAV to target membranes with a panel of DNA-lipids to investigate the effects of the distance and tether flexibility between virions and target membranes on the kinetics of IAV binding and fusion. Tether length and the presence of a flexible linker led to higher rates of IAV binding, while the efficiencies of lipid and content mixing were typically lower for longer and more rigid DNA tethers. For all DNA tether modifications, we found that the rates of IAV lipid and content mixing were unchanged. These results suggest that variations in the interface between IAV and a target membrane do not significantly impact the rate-limiting step of fusion or the low-pH-triggered engagement of viral fusion peptides with the target membrane. However, our results imply that the flexibility of the viral receptor is important for ensuring that hemifusion events are able to successfully proceed to pore formation.
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Affiliation(s)
- Elizabeth R Webster
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Katherine N Liu
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Robert J Rawle
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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36
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Cooperative Chikungunya Virus Membrane Fusion and Its Substoichiometric Inhibition by CHK-152 Antibody. Viruses 2022; 14:v14020270. [PMID: 35215863 PMCID: PMC8877538 DOI: 10.3390/v14020270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 01/18/2022] [Accepted: 01/25/2022] [Indexed: 11/17/2022] Open
Abstract
Chikungunya virus (CHIKV) presents a major burden on healthcare systems worldwide, but specific treatment remains unavailable. Attachment and fusion of CHIKV to the host cell membrane is mediated by the E1/E2 protein spikes. We used an in vitro single-particle fusion assay to study the effect of the potent, neutralizing antibody CHK-152 on CHIKV binding and fusion. We find that CHK-152 shields the virions, inhibiting interaction with the target membrane and inhibiting fusion. The analysis of the ratio of bound antibodies to epitopes implied that CHIKV fusion is a highly cooperative process. Further, dissociation of the antibody at lower pH results in a finely balanced kinetic competition between inhibition and fusion, suggesting a window of opportunity for the spike proteins to act and mediate fusion, even in the presence of the antibody.
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37
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Egloff S, Melnychuk N, Cruz Da Silva E, Reisch A, Martin S, Klymchenko AS. Amplified Fluorescence in Situ Hybridization by Small and Bright Dye-Loaded Polymeric Nanoparticles. ACS NANO 2022; 16:1381-1394. [PMID: 34928570 DOI: 10.1021/acsnano.1c09409] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Detection and imaging of RNA at the single-cell level is of utmost importance for fundamental research and clinical diagnostics. Current techniques of RNA analysis, including fluorescence in situ hybridization (FISH), are long, complex, and expensive. Here, we report a methodology of amplified FISH (AmpliFISH) that enables simpler and faster RNA imaging using small and ultrabright dye-loaded polymeric nanoparticles (NPs) functionalized with DNA. We found that the small size of NPs (below 20 nm) was essential for their access to the intracellular mRNA targets in fixed permeabilized cells. Moreover, proper selection of the polymer matrix of DNA-NPs minimized nonspecific intracellular interactions. Optimized DNA-NPs enabled sequence-specific imaging of different mRNA targets (survivin, actin, and polyA tails), using a simple 1 h staining protocol. Encapsulation of cyanine and rhodamine dyes with bulky counterions yielded green-, red-, and far-red-emitting NPs that were 2-100-fold brighter than corresponding quantum dots. These NPs enabled multiplexed detection of three mRNA targets simultaneously, showing distinctive mRNA expression profiles in three cancer cell lines. Image analysis confirmed the single-particle nature of the intracellular signal, suggesting single-molecule sensitivity of the method. AmpliFISH was found to be semiquantitative, correlating with RT-qPCR. In comparison with the commercial locked nucleic acid (LNA)-based FISH technique, AmpliFISH provides 8-200-fold stronger signal (dependent on the NP color) and requires only three steps vs ∼20 steps together with a much shorter time. Thus, combination of bright fluorescent polymeric NPs with FISH yields a fast and sensitive single-cell transcriptomic analysis method for RNA research and clinical diagnostics.
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Affiliation(s)
- Sylvie Egloff
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, 74, Route du Rhin, 67401 Illkirch, France
| | - Nina Melnychuk
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, 74, Route du Rhin, 67401 Illkirch, France
| | - Elisabete Cruz Da Silva
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, 74, Route du Rhin, 67401 Illkirch, France
| | - Andreas Reisch
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, 74, Route du Rhin, 67401 Illkirch, France
| | - Sophie Martin
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, 74, Route du Rhin, 67401 Illkirch, France
| | - Andrey S Klymchenko
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, 74, Route du Rhin, 67401 Illkirch, France
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38
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Tuerkova A, Kasson PM. Computational methods to study enveloped viral entry. Biochem Soc Trans 2021; 49:2527-2537. [PMID: 34783344 PMCID: PMC10184508 DOI: 10.1042/bst20210190] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 10/25/2021] [Accepted: 10/27/2021] [Indexed: 12/15/2022]
Abstract
The protein-membrane interactions that mediate viral infection occur via loosely ordered, transient assemblies, creating challenges for high-resolution structure determination. Computational methods and in particular molecular dynamics simulation have thus become important adjuncts for integrating experimental data, developing mechanistic models, and suggesting testable hypotheses regarding viral function. However, the large molecular scales of virus-host interaction also create challenges for detailed molecular simulation. For this reason, continuum membrane models have played a large historical role, although they have become less favored for high-resolution models of protein assemblies and lipid organization. Here, we review recent progress in the field, with an emphasis on the insight that has been gained using a mixture of coarse-grained and atomic-resolution molecular dynamics simulations. Based on successes and challenges to date, we suggest a multiresolution strategy that should yield the best mixture of computational efficiency and physical fidelity. This strategy may facilitate further simulations of viral entry by a broader range of viruses, helping illuminate the diversity of viral entry strategies and the essential common elements that can be targeted for antiviral therapies.
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Affiliation(s)
- Alzbeta Tuerkova
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
| | - Peter M Kasson
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, Uppsala 75124, Sweden
- Departments of Molecular Physiology and Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, U.S.A
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39
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Nicolson GL, Ferreira de Mattos G. A Brief Introduction to Some Aspects of the Fluid-Mosaic Model of Cell Membrane Structure and Its Importance in Membrane Lipid Replacement. MEMBRANES 2021; 11:947. [PMID: 34940448 PMCID: PMC8708848 DOI: 10.3390/membranes11120947] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 11/18/2021] [Accepted: 11/22/2021] [Indexed: 12/15/2022]
Abstract
Early cell membrane models placed most proteins external to lipid bilayers in trimolecular structures or as modular lipoprotein units. These thermodynamically untenable structures did not allow lipid lateral movements independent of membrane proteins. The Fluid-Mosaic Membrane Model accounted for these and other properties, such as membrane asymmetry, variable lateral mobilities of membrane components and their associations with dynamic complexes. Integral membrane proteins can transform into globular structures that are intercalated to various degrees into a heterogeneous lipid bilayer matrix. This simplified version of cell membrane structure was never proposed as the ultimate biomembrane description, but it provided a basic nanometer scale framework for membrane organization. Subsequently, the structures associated with membranes were considered, including peripheral membrane proteins, and cytoskeletal and extracellular matrix components that restricted lateral mobility. In addition, lipid-lipid and lipid-protein membrane domains, essential for cellular signaling, were proposed and eventually discovered. The presence of specialized membrane domains significantly reduced the extent of the fluid lipid matrix, so membranes have become more mosaic with some fluid areas over time. However, the fluid regions of membranes are very important in lipid transport and exchange. Various lipid globules, droplets, vesicles and other membranes can fuse to incorporate new lipids or expel damaged lipids from membranes, or they can be internalized in endosomes that eventually fuse with other internal vesicles and membranes. They can also be externalized in a reverse process and released as extracellular vesicles and exosomes. In this Special Issue, the use of membrane phospholipids to modify cellular membranes in order to modulate clinically relevant host properties is considered.
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Affiliation(s)
- Garth L. Nicolson
- Department of Molecular Pathology, The Institute for Molecular Medicine, Huntington Beach, CA 92647, USA
| | - Gonzalo Ferreira de Mattos
- Laboratory of Ion Channels, Biological Membranes and Cell Signaling, Department of Biophysics, Facultad de Medicina, Universidad de la República, Montevideo 11600, Uruguay;
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40
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Tang T, Savva A, Traberg WC, Xu C, Thiburce Q, Liu HY, Pappa AM, Martinelli E, Withers A, Cornelius M, Salleo A, Owens RM, Daniel S. Functional Infectious Nanoparticle Detector: Finding Viruses by Detecting Their Host Entry Functions Using Organic Bioelectronic Devices. ACS NANO 2021; 15:18142-18152. [PMID: 34694775 DOI: 10.1021/acsnano.1c06813] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Emerging viruses will continue to be a threat to human health and wellbeing into the foreseeable future. The COVID-19 pandemic revealed the necessity for rapid viral sensing and inhibitor screening in mitigating viral spread and impact. Here, we present a platform that uses a label-free electronic readout as well as a dual capability of optical (fluorescence) readout to sense the ability of a virus to bind and fuse with a host cell membrane, thereby sensing viral entry. This approach introduces a hitherto unseen level of specificity by distinguishing fusion-competent viruses from fusion-incompetent viruses. The ability to discern between competent and incompetent viruses means that this device could also be used for applications beyond detection, such as screening antiviral compounds for their ability to block virus entry mechanisms. Using optical means, we first demonstrate the ability to recapitulate the entry processes of influenza virus using a biomembrane containing the viral receptor that has been functionalized on a transparent organic bioelectronic device. Next, we detect virus membrane fusion, using the same, label-free devices. Using both reconstituted and native cell membranes as materials to functionalize organic bioelectronic devices, configured as electrodes and transistors, we measure changes in membrane properties when virus fusion is triggered by a pH drop, inducing hemagglutinin to undergo a conformational change that leads to membrane fusion.
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Affiliation(s)
- Tiffany Tang
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Olin Hall, Ithaca, New York 14853, United States
| | - Achilleas Savva
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB30AS Cambridge, United Kingdom
| | - Walther C Traberg
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB30AS Cambridge, United Kingdom
| | - Cheyan Xu
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Olin Hall, Ithaca, New York 14853, United States
| | - Quentin Thiburce
- Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, California 94305, United States
| | - Han-Yuan Liu
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Olin Hall, Ithaca, New York 14853, United States
| | - Anna-Maria Pappa
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB30AS Cambridge, United Kingdom
| | - Eleonora Martinelli
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB30AS Cambridge, United Kingdom
| | - Aimee Withers
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB30AS Cambridge, United Kingdom
| | - Mercedes Cornelius
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB30AS Cambridge, United Kingdom
| | - Alberto Salleo
- Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, California 94305, United States
| | - Róisín M Owens
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CB30AS Cambridge, United Kingdom
| | - Susan Daniel
- Robert F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Olin Hall, Ithaca, New York 14853, United States
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41
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Nikolaus J, Hancock K, Tsemperouli M, Baddeley D, Karatekin E. Optimal Detection of Fusion Pore Dynamics Using Polarized Total Internal Reflection Fluorescence Microscopy. Front Mol Biosci 2021; 8:740408. [PMID: 34859048 PMCID: PMC8631473 DOI: 10.3389/fmolb.2021.740408] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 10/06/2021] [Indexed: 11/13/2022] Open
Abstract
The fusion pore is the initial narrow connection that forms between fusing membranes. During vesicular release of hormones or neurotransmitters, the nanometer-sized fusion pore may open-close repeatedly (flicker) before resealing or dilating irreversibly, leading to kiss-and-run or full-fusion events, respectively. Pore dynamics govern vesicle cargo release and the mode of vesicle recycling, but the mechanisms are poorly understood. This is partly due to a lack of reconstituted assays that combine single-pore sensitivity and high time resolution. Total internal reflection fluorescence (TIRF) microscopy offers unique advantages for characterizing single membrane fusion events, but signals depend on effects that are difficult to disentangle, including the polarization of the excitation electric field, vesicle size, photobleaching, orientation of the excitation dipoles of the fluorophores with respect to the membrane, and the evanescent field depth. Commercial TIRF microscopes do not allow control of excitation polarization, further complicating analysis. To overcome these challenges, we built a polarization-controlled total internal reflection fluorescence (pTIRF) microscope and monitored fusion of proteoliposomes with planar lipid bilayers with single molecule sensitivity and ∼15 ms temporal resolution. Using pTIRF microscopy, we detected docking and fusion of fluorescently labeled small unilamellar vesicles, reconstituted with exocytotic/neuronal v-SNARE proteins (vSUVs), with a supported bilayer containing the cognate t-SNAREs (tSBL). By varying the excitation polarization angle, we were able to identify a dye-dependent optimal polarization at which the fluorescence increase upon fusion was maximal, facilitating event detection and analysis of lipid transfer kinetics. An improved algorithm allowed us to estimate the size of the fusing vSUV and the fusion pore openness (the fraction of time the pore is open) for every event. For most events, lipid transfer was much slower than expected for diffusion through an open pore, suggesting that fusion pore flickering limits lipid release. We find a weak correlation between fusion pore openness and vesicle area. The approach can be used to study mechanisms governing fusion pore dynamics in a wide range of membrane fusion processes.
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Affiliation(s)
- Joerg Nikolaus
- Cellular and Molecular Physiology, Yale University, New Haven, CT, United States
- Nanobiology Institute, Yale University, West Haven, CT, United States
| | - Kasey Hancock
- Cellular and Molecular Physiology, Yale University, New Haven, CT, United States
- Nanobiology Institute, Yale University, West Haven, CT, United States
- Integrated Physical and Engineering Biology Program, Yale University, New Haven, CT, United States
| | - Maria Tsemperouli
- Cellular and Molecular Physiology, Yale University, New Haven, CT, United States
- Nanobiology Institute, Yale University, West Haven, CT, United States
| | - David Baddeley
- Nanobiology Institute, Yale University, West Haven, CT, United States
- Cell Biology, Yale University, New Haven, CT, United States
| | - Erdem Karatekin
- Cellular and Molecular Physiology, Yale University, New Haven, CT, United States
- Nanobiology Institute, Yale University, West Haven, CT, United States
- Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, United States
- Saints-Pères Paris Institute for the Neurosciences (SPPIN), Université de Paris, Centre National de la Recherche Scientifique (CNRS), Paris, France
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42
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Liu KN, Boxer SG. Single-virus content-mixing assay reveals cholesterol-enhanced influenza membrane fusion efficiency. Biophys J 2021; 120:4832-4841. [PMID: 34536389 DOI: 10.1016/j.bpj.2021.09.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 08/05/2021] [Accepted: 09/09/2021] [Indexed: 10/20/2022] Open
Abstract
To infect a cell, enveloped viruses must first undergo membrane fusion, which proceeds through a hemifusion intermediate, followed by the formation of a fusion pore through which the viral genome is transferred to a target cell. Single-virus fusion studies to elucidate the dynamics of content mixing typically require extensive fluorescent labeling of viral contents. The labeling process must be optimized depending on the virus identity and strain and can potentially be perturbative to viral fusion behavior. Here, we introduce a single-virus assay in which content-labeled vesicles are bound to unlabeled influenza A virus (IAV) to eliminate the problematic step of content-labeling virions. We use fluorescence microscopy to observe individual, pH-triggered content mixing and content-loss events between IAV and target vesicles of varying cholesterol compositions. We show that target membrane cholesterol increases the efficiency of IAV content mixing and decreases the fraction of content-mixing events that result in content loss. These results are consistent with previous findings that cholesterol stabilizes pore formation in IAV entry and limits leakage after pore formation. We also show that content loss due to hemagglutinin fusion peptide engagement with the target membrane is independent of composition. This approach is a promising strategy for studying the single-virus content-mixing kinetics of other enveloped viruses.
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Affiliation(s)
- Katherine N Liu
- Department of Chemistry, Stanford University, Stanford, California
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California.
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43
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Bally M, Block S, Höök F, Larson G, Parveen N, Rydell GE. Physicochemical tools for studying virus interactions with targeted cell membranes in a molecular and spatiotemporally resolved context. Anal Bioanal Chem 2021; 413:7157-7178. [PMID: 34490501 PMCID: PMC8421089 DOI: 10.1007/s00216-021-03510-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 06/23/2021] [Accepted: 06/28/2021] [Indexed: 12/14/2022]
Abstract
The objective of this critical review is to provide an overview of how emerging bioanalytical techniques are expanding our understanding of the complex physicochemical nature of virus interactions with host cell surfaces. Herein, selected model viruses representing both non-enveloped (simian virus 40 and human norovirus) and enveloped (influenza A virus, human herpes simplex virus, and human immunodeficiency virus type 1) viruses are highlighted. The technologies covered utilize a wide range of cell membrane mimics, from supported lipid bilayers (SLBs) containing a single purified host membrane component to SLBs derived from the plasma membrane of a target cell, which can be compared with live-cell experiments to better understand the role of individual interaction pairs in virus attachment and entry. These platforms are used to quantify binding strengths, residence times, diffusion characteristics, and binding kinetics down to the single virus particle and single receptor, and even to provide assessments of multivalent interactions. The technologies covered herein are surface plasmon resonance (SPR), quartz crystal microbalance with dissipation (QCM-D), dynamic force spectroscopy (DFS), total internal reflection fluorescence (TIRF) microscopy combined with equilibrium fluctuation analysis (EFA) and single particle tracking (SPT), and finally confocal microscopy using multi-labeling techniques to visualize entry of individual virus particles in live cells. Considering the growing scientific and societal needs for untangling, and interfering with, the complex mechanisms of virus binding and entry, we hope that this review will stimulate the community to implement these emerging tools and strategies in conjunction with more traditional methods. The gained knowledge will not only contribute to a better understanding of the virus biology, but may also facilitate the design of effective inhibitors to block virus entry.
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Affiliation(s)
- Marta Bally
- Department of Clinical Microbiology & Wallenberg Centre for Molecular Medicine, Umeå University, 901 85, Umeå, Sweden
| | - Stephan Block
- Department of Chemistry and Biochemistry, Freie Universität Berlin, 14195, Berlin, Germany
| | - Fredrik Höök
- Department of Physics, Chalmers University of Technology, 412 96, Gothenburg, Sweden.
| | - Göran Larson
- Department of Laboratory Medicine, Sahlgrenska Academy at the University of Gothenburg, Sahlgrenska University Hospital, Bruna Stråket 16, 413 45, Gothenburg, Sweden.
| | - Nagma Parveen
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India
| | - Gustaf E Rydell
- Department of Infectious Diseases, Sahlgrenska Academy at the University of Gothenburg, 413 46, Gothenburg, Sweden
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44
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HIV-1 Entry and Membrane Fusion Inhibitors. Viruses 2021; 13:v13050735. [PMID: 33922579 PMCID: PMC8146413 DOI: 10.3390/v13050735] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 04/13/2021] [Accepted: 04/21/2021] [Indexed: 12/14/2022] Open
Abstract
HIV-1 (human immunodeficiency virus type 1) infection begins with the attachment of the virion to a host cell by its envelope glycoprotein (Env), which subsequently induces fusion of viral and cell membranes to allow viral entry. Upon binding to primary receptor CD4 and coreceptor (e.g., chemokine receptor CCR5 or CXCR4), Env undergoes large conformational changes and unleashes its fusogenic potential to drive the membrane fusion. The structural biology of HIV-1 Env and its complexes with the cellular receptors not only has advanced our knowledge of the molecular mechanism of how HIV-1 enters the host cells but also provided a structural basis for the rational design of fusion inhibitors as potential antiviral therapeutics. In this review, we summarize our latest understanding of the HIV-1 membrane fusion process and discuss related therapeutic strategies to block viral entry.
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45
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Lanz C, Schotsaert M, Magnus C, Karakus U, Hunziker A, Sempere Borau M, Martínez-Romero C, Spieler EE, Günther SC, Moritz E, Hale BG, Trkola A, García-Sastre A, Stertz S. IFITM3 incorporation sensitizes influenza A virus to antibody-mediated neutralization. J Exp Med 2021; 218:212014. [PMID: 33882122 PMCID: PMC8072448 DOI: 10.1084/jem.20200303] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 02/02/2021] [Accepted: 03/04/2021] [Indexed: 12/17/2022] Open
Abstract
The disease severity of influenza is highly variable in humans, and one genetic determinant behind these differences is the IFITM3 gene. As an effector of the interferon response, IFITM3 potently blocks cytosolic entry of influenza A virus (IAV). Here, we reveal a novel level of inhibition by IFITM3 in vivo: We show that incorporation of IFITM3 into IAV particles competes with incorporation of viral hemagglutinin (HA). Decreased virion HA levels did not reduce infectivity, suggesting that high HA density on IAV virions may be an antagonistic strategy used by the virus to prevent direct inhibition. However, we found that IFITM3-mediated reduction in HA content sensitizes IAV to antibody-mediated neutralization. Mathematical modeling predicted that this effect decreases and delays peak IAV titers, and we show that, indeed, IFITM3-mediated sensitization of IAV to antibody-mediated neutralization impacts infection outcome in an in vivo mouse model. Overall, our data describe a previously unappreciated interplay between the innate effector IFITM3 and the adaptive immune response.
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Affiliation(s)
- Caroline Lanz
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland.,Life Sciences Zurich Graduate School, Eidgenössische Technische Hochschule Zurich and University of Zurich, Zurich, Switzerland
| | - Michael Schotsaert
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY.,Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Carsten Magnus
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland.,Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule Zurich, Basel, Switzerland.,Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Umut Karakus
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland
| | - Annika Hunziker
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland.,Life Sciences Zurich Graduate School, Eidgenössische Technische Hochschule Zurich and University of Zurich, Zurich, Switzerland
| | - Milagros Sempere Borau
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland.,Life Sciences Zurich Graduate School, Eidgenössische Technische Hochschule Zurich and University of Zurich, Zurich, Switzerland
| | - Carles Martínez-Romero
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY.,Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Eva E Spieler
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland.,Life Sciences Zurich Graduate School, Eidgenössische Technische Hochschule Zurich and University of Zurich, Zurich, Switzerland
| | - Sira C Günther
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland.,Life Sciences Zurich Graduate School, Eidgenössische Technische Hochschule Zurich and University of Zurich, Zurich, Switzerland
| | - Eva Moritz
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland
| | - Benjamin G Hale
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland
| | - Alexandra Trkola
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland
| | - Adolfo García-Sastre
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY.,Global Health and Emerging Pathogens Institute, Icahn School of Medicine at Mount Sinai, New York, NY.,Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY.,The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Silke Stertz
- Institute of Medical Virology, University of Zurich, Zurich, Switzerland
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46
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Castro M, Lythe G, Smit J, Molina-París C. Fusion and fission events regulate endosome maturation and viral escape. Sci Rep 2021; 11:7845. [PMID: 33846408 PMCID: PMC8041880 DOI: 10.1038/s41598-021-86877-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 03/15/2021] [Indexed: 02/08/2023] Open
Abstract
Endosomes are intracellular vesicles that mediate the communication of the cell with its extracellular environment. They are an essential part of the cell’s machinery regulating intracellular trafficking via the endocytic pathway. Many viruses, which in order to replicate require a host cell, attach themselves to the cellular membrane; an event which usually initiates uptake of a viral particle through the endocytic pathway. In this way viruses hijack endosomes for their journey towards intracellular sites of replication and avoid degradation without host detection by escaping the endosomal compartment. Recent experimental techniques have defined the role of endosomal maturation in the ability of enveloped viruses to release their genetic material into the cytoplasm. Endosome maturation depends on a family of small hydrolase enzymes (or GTPases) called Rab proteins, arranged on the cytoplasmic surface of its membrane. Here, we model endosomes as intracellular compartments described by two variables (its levels of active Rab5 and Rab7 proteins) and which can undergo coagulation (or fusion) and fragmentation (or fission). The key element in our approach is the “per-cell endosomal distribution” and its dynamical (Boltzmann) equation. The Boltzmann equation allows us to derive the dynamics of the total number of endosomes in a cell, as well as the mean and the standard deviation of its active Rab5 and Rab7 levels. We compare our mathematical results with experiments of Dengue viral escape from endosomes. The relationship between endosomal active Rab levels and pH suggests a mechanism that can account for the observed variability in viral escape times, which in turn regulate the viability of a viral intracellular infection.
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Affiliation(s)
- Mario Castro
- Grupo Interdisciplinar de Sistemas Complejos (GISC) and Instituto de Investigación Tecnológica (IIT), Universidad Pontificia Comillas, Madrid, Spain.
| | - Grant Lythe
- Department of Applied Mathematics, School of Mathematics, University of Leeds, Leeds, UK
| | - Jolanda Smit
- Department of Medical Microbiology and Infection Prevention, University Medical Center Groningen, Groningen, The Netherlands
| | - Carmen Molina-París
- Department of Applied Mathematics, School of Mathematics, University of Leeds, Leeds, UK. .,Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
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47
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Li T, Li Z, Deans EE, Mittler E, Liu M, Chandran K, Ivanovic T. The shape of pleomorphic virions determines resistance to cell-entry pressure. Nat Microbiol 2021; 6:617-629. [PMID: 33737748 DOI: 10.1038/s41564-021-00877-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 02/10/2021] [Indexed: 11/09/2022]
Abstract
Many enveloped animal viruses produce a variety of particle shapes, ranging from small spherical to long filamentous types. Characterization of how the shape of the virion affects infectivity has been difficult because the shape is only partially genetically encoded, and most pleomorphic virus structures have no selective advantage in vitro. Here, we apply virus fractionation using low-force sedimentation, as well as antibody neutralization coupled with RNAScope, single-particle membrane fusion experiments and stochastic simulations to evaluate the effects of differently shaped influenza A viruses and influenza viruses pseudotyped with Ebola glycoprotein on the infection of cells. Our results reveal that the shape of the virus particles determines the probability of both virus attachment and membrane fusion when viral glycoprotein activity is compromised. The larger contact interface between a cell and a larger particle offers a greater probability that several active glycoproteins are adjacent to each other and can cooperate to induce membrane merger. Particles with a length of tens of micrometres can fuse even when 95% of the glycoproteins are inactivated. We hypothesize that non-genetically encoded variable particle shapes enable pleomorphic viruses to overcome selective pressure and may enable adaptation to infection of cells by emerging viruses such as Ebola. Our results suggest that therapeutics targeting filamentous virus particles could overcome antiviral drug resistance and immune evasion in pleomorphic viruses.
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Affiliation(s)
- Tian Li
- Biochemistry Department, Brandeis University, Waltham, MA, USA
| | - Zhenyu Li
- Biochemistry Department, Brandeis University, Waltham, MA, USA
| | - Erin E Deans
- Biochemistry Department, Brandeis University, Waltham, MA, USA
| | - Eva Mittler
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, NY, USA
| | - Meisui Liu
- Biochemistry Department, Brandeis University, Waltham, MA, USA
| | - Kartik Chandran
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, NY, USA
| | - Tijana Ivanovic
- Biochemistry Department, Brandeis University, Waltham, MA, USA.
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48
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Mühlenbrock P, Sari M, Steinem C. In vitro single vesicle fusion assays based on pore-spanning membranes: merits and drawbacks. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2021; 50:239-252. [PMID: 33320298 PMCID: PMC8071798 DOI: 10.1007/s00249-020-01479-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 12/22/2022]
Abstract
Neuronal fusion mediated by soluble N-ethylmaleimide-sensitive-factor attachment protein receptors (SNAREs) is a fundamental cellular process by which two initially distinct membranes merge resulting in one interconnected structure to release neurotransmitters into the presynaptic cleft. To get access to the different stages of the fusion process, several in vitro assays have been developed. In this review, we provide a short overview of the current in vitro single vesicle fusion assays. Among those assays, we developed a single vesicle assay based on pore-spanning membranes (PSMs) on micrometre-sized pores in silicon, which might overcome some of the drawbacks associated with the other membrane architectures used for investigating fusion processes. Prepared by spreading of giant unilamellar vesicles with reconstituted t-SNAREs, PSMs provide an alternative tool to supported lipid bilayers to measure single vesicle fusion events by means of fluorescence microscopy. Here, we discuss the diffusive behaviour of the reconstituted membrane components as well as that of the fusing synthetic vesicles with reconstituted synaptobrevin 2 (v-SNARE). We compare our results with those obtained if the synthetic vesicles are replaced by natural chromaffin granules under otherwise identical conditions. The fusion efficiency as well as the different fusion states observable in this assay by means of both lipid mixing and content release are illuminated.
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Affiliation(s)
- Peter Mühlenbrock
- Georg-August-Universität Göttingen, Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077, Göttingen, Germany
| | - Merve Sari
- Georg-August-Universität Göttingen, Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077, Göttingen, Germany
| | - Claudia Steinem
- Georg-August-Universität Göttingen, Institute of Organic and Biomolecular Chemistry, Tammannstr. 2, 37077, Göttingen, Germany.
- Max-Planck-Institute for Dynamics and Self Organization, Am Faßberg 17, 37077, Göttingen, Germany.
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49
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Abstract
Genome transfer from a virus into a cell is a critical early step in viral replication. Enveloped viruses achieve the delivery of their genomes into the cytoplasm by merging the viral membrane with the cellular membrane via a conceptually simple mechanism called membrane fusion. In contrast, genome translocation mechanisms in nonenveloped viruses, which lack viral membranes, remain poorly understood. Although cellular assays provide useful information about cell entry and genome release, it is difficult to obtain detailed mechanistic insights due both to the inherent technical difficulties associated with direct visualization of these processes and to the prevalence of nonproductive events in cellular assays performed at a very high multiplicity of infection. To overcome these issues, we developed an in vitro single-particle fluorescence assay to characterize genome release from a nonenveloped virus (poliovirus) in real time using a tethered receptor-decorated liposome system. Our results suggest that poliovirus genome release is a complex process that consists of multiple rate-limiting steps. Interestingly, we found that the addition of exogenous wild-type capsid protein VP4, but not mutant VP4, enhanced the efficiency of genome translocation. These results, together with prior structural analysis, suggest that VP4 interacts with RNA directly and forms a protective, membrane-spanning channel during genome translocation. Furthermore, our data indicate that VP4 dynamically interacts with RNA, rather than forming a static tube for RNA translocation. This study provides new insights into poliovirus genome translocation and offers a cell-free assay that can be utilized broadly to investigate genome release processes in other nonenveloped viruses.
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Touizer E, Sieben C, Henriques R, Marsh M, Laine RF. Application of Super-Resolution and Advanced Quantitative Microscopy to the Spatio-Temporal Analysis of Influenza Virus Replication. Viruses 2021; 13:233. [PMID: 33540739 PMCID: PMC7912985 DOI: 10.3390/v13020233] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 01/28/2021] [Accepted: 01/28/2021] [Indexed: 02/07/2023] Open
Abstract
With an estimated three to five million human cases annually and the potential to infect domestic and wild animal populations, influenza viruses are one of the greatest health and economic burdens to our society, and pose an ongoing threat of large-scale pandemics. Despite our knowledge of many important aspects of influenza virus biology, there is still much to learn about how influenza viruses replicate in infected cells, for instance, how they use entry receptors or exploit host cell trafficking pathways. These gaps in our knowledge are due, in part, to the difficulty of directly observing viruses in living cells. In recent years, advances in light microscopy, including super-resolution microscopy and single-molecule imaging, have enabled many viral replication steps to be visualised dynamically in living cells. In particular, the ability to track single virions and their components, in real time, now allows specific pathways to be interrogated, providing new insights to various aspects of the virus-host cell interaction. In this review, we discuss how state-of-the-art imaging technologies, notably quantitative live-cell and super-resolution microscopy, are providing new nanoscale and molecular insights into influenza virus replication and revealing new opportunities for developing antiviral strategies.
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Affiliation(s)
- Emma Touizer
- Division of Infection and Immunity, University College London, London WC1E 6AE, UK;
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK; (R.H.); (M.M.)
| | - Christian Sieben
- Department of Cell Biology, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany;
| | - Ricardo Henriques
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK; (R.H.); (M.M.)
- The Francis Crick Institute, London NW1 1AT, UK
- Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal
| | - Mark Marsh
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK; (R.H.); (M.M.)
| | - Romain F. Laine
- MRC Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK; (R.H.); (M.M.)
- The Francis Crick Institute, London NW1 1AT, UK
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